The ion milling device is a device that smoothly mills a sample without any stress with the use of a physical sputtering phenomenon in which ions of argon or the like generated within an anode are accelerated to about 10 kV or lower (in order to reduce a damage on the sample), and the sample is irradiated with the ions not converged to sputter sample atoms from a sample surface.
The amount of sample milled by irradiating the sample with an ion beam depends on composition of the sample, an irradiation angle of the ion beam, a crystal orientation, or an acceleration voltage of the ion. However, when the sample is set so that the irradiation angle of the ion beam becomes 90 degrees, a difference in the milled amount depending on the composition of the sample can be reduced, and a multi-layer film of multiple composition can be also smoothly processed.
In this situation, in the irradiation of the sample with the ion beam, in order to prevent a position other than an ion milling target position from being irradiated with the ion beam, a plate (hereinafter also called “shield” or “mask”) for blocking the ion beam is arranged in the ion beam irradiation direction (note: ion source side=ion gun side) of the sample at a processing target position. The sample is exposed from the shield by several hundred microns or lower, and irradiated with the ion beam, and an exposed sample portion is physically sputtered, and milled, to thereby obtain a smooth sample surface.
PTL 1 discloses that a micrometer for regulating a mask position is disposed for the purpose of accurately setting a processing area (exposed area of the sample to the ion beam).